1. Field of the Invention
This invention relates to sprocket chains, and more particularly, to an improved chain link construction for such a chain and method for forming the same.
2. Description of the Prior Art
Relatively inexpensive drive or sprocket chains suitable for any type of transmission and conveyor purposes are in great demand since they are capable of a wide variety of applications in modern industry. Such chains are frequently used under very difficult running conditions with regular maintenance at a minimum. These chains are also used outdoors where weather and abrasion factors become a problem. One broad field of application for such chains occurs in various types of agricultural machinery. It is therefore highly desirable to provide a chain link that is both relatively inexpensive to manufacture and has good durability under such conditions.
While prior art chains have been sufficient for the equipment of the past, the sophisticated needs of the modern farmer require that better chains be used. Prior art chain links have been made from blanks formed from materials sheared from one end of the blank or from material sheared from the inside of the blank. This shearing creates sharp corners which, in turn, create crack propagation sites at the intersection of the barrel with the remainder of the chain link. Also, prior art chain links have included pin portions having similar crack propogation sites associated therewith. These crack propogation sites facilitate the formation of cracks during normal use with the result being a premature failure of the chain link. Thus, it is highly desirable to provide a chain link having a relative scarcity of crack propogation sites adjacent both the barrel and pin portions thereof.
In those prior art chain links in which one end of the blank is formed into a barrel of an almost completely circular configuration, the working of the blank associated with the formation of the one-piece barrel or the assembly or disassembly of a link may cause the barrel to become embrittled. This embrittlement also can facilitate the premature failure of the link during operation. Thus, it is highly desirable to provide a chain link minimizing such embrittlement characteristics in the barrel thereof.
Those prior art chain links in which one end of the blank is formed into a barrel of an almost completely circular configuration also are limited with regard to the gauge of the steel from which the links can be made. Thus, it is highly desirable to provide such a chain link which can be made of heavier gauge steel than heretofore possible.
The barrel of prior art one-piece barrel chain links is generally sheared from one end or the inside of a blank. Consequently, when the chain is driven is in both directions reversed, the pins of the links ride against the free end of the barrel and the chain link often fails for one of two reasons. In some situations, pressure exerted by the pin causes the free end of the barrel to lift up which allows the pin to be disengaged from the barrel. In other situations, the pressure exerted by the pin will cause the barrel to pull out from the remainder of the chain link due to the fact that it is sheared from the inside of the blank and the applied stress is parallel to the direction in which the barrel was formed. When the chain is driven in only one direction these problems are not as severe. However, with the increased sophistication of modern industry, often times chains are required to handle operating stresses when driven in both clockwise and counterclockwise directions. Thus, it would be highly desirable to provide an improved chain link having a barrel that can withstand operating stresses when driven in both clockwise or counterclockwise directions.